1. Field of the Invention
The invention pertains to a tubular body, especially for the joint eye holding a piston cylinder unit, which is formed from a sheet metal blank.
2. Description of the Related Art
An outer tubular body is required for the production of a joint eye. This tubular body can be produced from blanks of various types. Blanks which are cut to length from a tube are widely used. Because semi-finished tubular materials are comparatively expensive, alternative tubular bodies made from sheet-metal blanks have been in use for some time. A joint eye of this type is known from, for example, EP 0 884 501 A1. An area where a threaded rod can be connected is also provided on this joint eye. All joint eyes of this basic design, however, suffer from the problem that the amount of tensile force which can be transmitted depends on the load capacity of the weld which joins the rolled-up ends of the sheet-metal blank which has been formed into the tubular body. The load is transmitted to the joint eye in these cases by a load-transfer pin (not shown), which is parallel to the weld.
The object of the present invention is to realize a joint eye which combines the cost advantage of the rolled tubular body with the strength of the tubular body obtained by cutting a tube to length.
In accordance with the invention, the sheet-metal blank has at least two stamped circumferentially closed sleeve parts, which are connected to each other by a single connecting web. In the final fabrication state, the sleeve parts are coaxially arranged, one next to the other, with the end surfaces of the sleeve parts facing each other to form circumferentially closed joint eye.
The advantage of the invention is that there is no load-determining weld in the direction transverse to the tubular body. It is possible to use a very simple sheet-metal blank, which is much cheaper than a semi-finished product in the form of drawn tubing. In addition, only certain diameters and wall thicknesses of drawn tubing are commercially available. Such limitations no longer apply when the tubular body is made as a stamped and pressed part.
When it is desired to connect the adjacent sleeve parts to each other, it is possible to press a spring element and/or a damping element into the sleeve parts, which spring or damping element can also have axial stops to hold the sleeve parts together under tension.
So that the spring element and/or damping element can be installed easily and with reduced stress, it is advantageous to stamp transition surfaces into the ends of the sleeve parts opposite the facing end surfaces, these transition surfaces leading to the inside walls of the sleeve parts. The stamping process for producing the transition surface is virtually cost-neutral in comparison to the machining of a cut-to-length tubular body.
There is also the possibility of welding the sleeve parts together.
So that a connection can be established with an assembly such as the piston rod or cylinder of a piston-cylinder unit, it is provided that a pass-through opening for a fastening connector is stamped into the connecting web.
As a logical elaboration, at least the largest length section of the sleeve parts extends from the plane of the connecting web to the end surface. It is thus possible to provide a longer connecting web. The forming tools for the metal-forming process which determine the bending radii and the bending points can thus be inserted more easily, and larger bending radii can be allowed.
According to a preferred embodiment, the pass-through opening has an area of expanded diameter at the end next to the facing sleeve parts. The sleeve parts which are in contact with each other form the boundaries of the pass-through opening. As a result, the area of expanded diameter represents a kind of xe2x80x9cclearingxe2x80x9d for a connector body, such as the thread on the piston rod mentioned above.
So that the tubular body can be connected more easily to an assembly by means of, for example, a threaded element, flat surfaces (flats) for a wrench are stamped on opposite side edges of the connecting web in the area of the pass-through opening, These flat surfaces have transitions to the adjacent sides.
There is in principle the option of providing the connecting web with a transverse web, which can serve as a retainer in the final fabrication state of the tubular body. In the case of a tubular body for a joint eye of a piston-cylinder unit, one could imagine this retainer as, for example, a brake line holder.
In an alternative solution, the tubular body is stamped from a flat sheet-metal blank and has at each end a stamped-in transition surface to the inside wall of the tubular body. Thus a tubular body without a weld is again obtained, which has individually specified dimensions and is ready to be used with already stamped-in transition surfaces as it comes from the die set.
It is also advantageous for the tubular body to be provided on at least one end, in the area of the outside wall, with a sheared edge around the circumference, obtained by cutting off the border. Thus a clearly defined external contour is obtained, which meets elevated requirements on visual appearance.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.